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lion eats fox
fox eats hare
hare eats carrot.

static  Function  pairMap(BiFunction mapper)
{
return new Function () {
T previous = null;
boolean hasPrevious;

public Stream apply(T t)
{
Stream result;
if(!hasPrevious)
{
hasPrevious = true;
result = Stream.empty();
}
else
{
result = Stream.of(mapper.apply(previous, t));
}
previous = t;
return result;
}
};
}
static  Stream getAdjecentOverlappingStream(List list)
{
return list.stream().flatMap(pairMap((a,b) -> a+" eats "+ b));
}

//consider the class name I am working with is StreamUtils.
StreamUtils.getAdjecentOverlappingStream(Arrays.asList("lion","fox","hare","carrot"))
.forEach(System.out::println);;

StreamLecture.java:83: error: cannot infer type arguments for Function
return new Function () {
^
reason: cannot use '' with anonymous inner classes
where T,R are type-variables:
T extends Object declared in interface Function
R extends Object declared in interface Function
StreamLecture.java:106: error: incompatible types: inference variable R#1 has incompatible bounds
return list.stream().flatMap(pairMap((a,b) -> a+" eats "+ b));
^
equality constraints: T#2
lower bounds: String,R#2
where R#1,T#1,T#2,R#2,T#3 are type-variables:
R#1 extends Object declared in method flatMap(Function

Ich arbeite an einem Problem, bei dem ich überlappende Paare aus dem Stream verarbeiten muss.
Betrachten Sie zum Beispiel die Liste → ["Löwe", "Fuchs", "Hase" ,"carrot"].
Die Ausgabe wird sein:
[code]lion eats fox
fox eats hare
hare eats carrot.
[/code]
Die Ausgabeelemente sind immer um eins kleiner als die der ursprünglichen Liste. Ich verwende derzeit Java 8. Hier ist mein Code:
Code
[code]static Function pairMap(BiFunction mapper)
{
return new Function () {
T previous = null;
boolean hasPrevious;

public Stream apply(T t)
{
Stream result;
if(!hasPrevious)
{
hasPrevious = true;
result = Stream.empty();
}
else
{
result = Stream.of(mapper.apply(previous, t));
}
previous = t;
return result;
}
};
}
static Stream getAdjecentOverlappingStream(List list)
{
return list.stream().flatMap(pairMap((a,b) -> a+" eats "+ b));
}

[/code]
Aufrufende Methode
[code]//consider the class name I am working with is StreamUtils.
StreamUtils.getAdjecentOverlappingStream(Arrays.asList("lion","fox","hare","carrot"))
.forEach(System.out::println);;
[/code]
Aber dieser Code gibt mir den Fehler [b]Fehler: Typargumente für Funktion können nicht abgeleitet werden[/b]
Siehe Vollständiger Fehler.
Fehler
[code]StreamLecture.java:83: error: cannot infer type arguments for Function
return new Function () {
^
reason: cannot use '' with anonymous inner classes
where T,R are type-variables:
T extends Object declared in interface Function
R extends Object declared in interface Function
StreamLecture.java:106: error: incompatible types: inference variable R#1 has incompatible bounds
return list.stream().flatMap(pairMap((a,b) -> a+" eats "+ b));
^
equality constraints: T#2
lower bounds: String,R#2
where R#1,T#1,T#2,R#2,T#3 are type-variables:
R#1 extends Object declared in method flatMap(Function